The present invention relates to mobile communications equipment. More particularly, the present invention relates to mobile communications equipment which is well suited to a case where a communications terminal moves out of a service area or to a case where it is connectible to a plurality of sorts of network.
In mobile communications, a radio channel for communication is established between a mobile communications terminal which moves on the ground, on the sea or in the sky and a base station or relay station which is fixed, e.g., on the ground or a satellite which is revolving round the earth. Whenever the base station or the like is located within a range in which a radio signal is reachable, the mobile communications terminal can be connected with the channel for both call origination and call termination. In a case where the mobile communications terminal is moving within such a service area, the user thereof need not especially worry about being able to talk. Since, however, base stations are not installed in all areas, the mobile communications terminal might move out of the service area. When the mobile terminal has moved out of the service area in this manner, a display is commonly presented on a display unit or the like to indicate that the mobile terminal currently lies in an area where communication is impossible.
With the conventional mobile communications terminal as stated above, unless the user looks at the display, he/she cannot judge whether or not the terminal is currently in the service area. In a case where the user wants to communicate while walking or while moving aboard an automobile or streetcar by way of example, he/she first checks the display of the mobile communications terminal. When the display indicates "outside the service area", the user abandons the desired communication. Thereafter, he/she needs to look at the display unit again and again in order to check if the terminal has entered the service area in which communication is possible. This is rather troublesome for the user. Especially when driving the automobile, the operation of checking the display can hamper the driving movement and is a serious hazard to safety.
Besides, in the case of a personal telephone set whose communicable range is as narrow as 10 [meters].about. several hundred [meters], it is quite natural that the user will pass the service area without noticing his/her entry even when he/she is walking.
Techniques intended to solve the above drawbacks are disclosed in Japanese Patent Applications Laid-open No. 318326/1989, No. 250727/1992,No. 314442/1989 and No. 207724/1992. With each of the techniques stated in Japanese Patent Applications Laid-open No. 318326/1989 and No. 314442/1989, the first audible sound is generated when it is decided that a mobile communications equipment is lying inside the service area of a base station on the basis of a signal transmitted from the base station, and the second audible sound is generated when it is decided that the equipment is lying outside the service area. Thus, the user of the mobile communications equipment can be reliably informed as to whether or not the equipment lies within the service area. In addition, the technique stated in Japanese Patent Application Laid-open No. 250727/1992 provides reception means for detecting a communicable state through a base station, and transfer means adapted to turn "on" in accordance with a communicability signal detected by the reception means, for transferring the communicable state in terms of notification expedients such as a sound, a display and vibrations. In this way, the presence of the base station can be automatically made known through the use of the five senses in a car or on the street. Further, with the technique stated in Japanese Patent Application Laid-open No. 207724/1992, the reception levels of a plurality of sorts of signals from a transmitter are detected for deciding the quality of a reception state, the duration for which the reception state is decided to be no good is compared with a preset time period, and an output signal is produced when the duration has exceeded the preset time period.
With any of the above-described techniques, the user is notified that the mobile communications equipment has fallen into the communicable state. In this regard, even when not necessary, the notification is given whenever the communicable state has been established. That is, even when the user does not want to originate a call with the mobile communications equipment, he/she is notified. Accordingly, in the case where the notifying sound (beep) is used by way of example, it is useless information and is noisy.
Furthermore, increase in network offerers is expected owing to the progress of communications networks in the future. In this case, service contents, charges for communications, etc. might become different,depending upon the offerers of network, and users will select the type of to use. Nevertheless, the above-described techniques have not provided any convenient means for selecting one of the networks and for deciding whether or not the selected network is communicable.